step-5 XHR and dependency injection

- Replaced the in-memory dataset with data loaded from the server (in
  the form of static phone.json file to make this tutorial backend
  agnostic)
  - The json file is loaded using the [$http] service
- Demonstrate the use of [services][service] and [dependency injection][DI]
  - The [$http] is injected into the controller through [dependency injection][DI]